Add tests for helper_metadata to TransportMessage and TransportEvent tests.
Add tests for helper_metadata to TransportMessage and TransportEvent tests.

vishwaprakashmishra/xmatrix,harrissoerja/vumi,harrissoerja/vumi,vishwaprakashmishra/xmatrix,TouK/vumi,TouK/vumi,vishwaprakashmishra/xmatrix,harrissoerja/vumi,TouK/vumi